Concurrency Limit Configuration

Deprecated

The concurrency limit filter has been deprecated for most scenarios. Developers should instead specify a ConcurrentMessageLimit at the bus, endpoint, or consumer level to limit the number of messages processed concurrently.

The concurrency limit filter supports any pipe context (any type that implements PipeContext, which includes most *Context types in MassTransit). For this reason alone the filter still exists in MassTransit despite being deprecated in concurrent message limit scenarios.

Configure a concurrency limit

The recommended approach is to use ConcurrentMessageLimit at the appropriate level.

On the bus

services.AddMassTransit(x =>
{
    x.UsingRabbitMq((context, cfg) =>
    {
        cfg.Host("localhost");

        cfg.ConcurrentMessageLimit = 8;

        cfg.ConfigureEndpoints(context);
    });
});

On a receive endpoint

cfg.ReceiveEndpoint("input-queue", e =>
{
    e.ConcurrentMessageLimit = 4;

    e.ConfigureConsumer<MyConsumer>(context);
});

In a consumer definition

services.AddMassTransit(x =>
{
    x.AddConsumer<MyConsumer, MyConsumerDefinition>();

    x.UsingRabbitMq((context, cfg) =>
    {
        cfg.ConfigureEndpoints(context);
    });
});

public class MyConsumerDefinition : ConsumerDefinition<MyConsumer>
{
    protected override void ConfigureConsumer(IReceiveEndpointConfigurator endpointConfigurator, IConsumerConfigurator<MyConsumer> consumerConfigurator)
    {
        endpointConfigurator.ConcurrentMessageLimit = 4;
    }
}

Using the deprecated filter

If you still need to use the concurrency limit filter (for example, for non-standard scenarios):

cfg.ReceiveEndpoint("submit-order", e =>
{
    e.UseConcurrencyLimit(4);

    e.ConfigureConsumer<SubmitOrderConsumer>(context);
});

The filter supports any pipe context, making it useful for scenarios beyond message consumption, such as limiting concurrency in send or publish pipelines.